Methods of preparing compressed explosive charges



' be the form of the shell.

7 means Patented Nov. 21, l fil 3,009,386 METHODS OF PREPG COMPRESSED EXPLOSIVE CHARGES Alexandre Billard, Paris, France, assiguor to Societe dExploitation des Materiels Hispano-Suiza, Bois-Colombes (Seine), (France No Drawing. Filed Oct. 21, 1957, Ser. No. 691,149 Claims priority, application France Oct. 22, 1956 2 Claims. (Cl. 86-20) The present invention relates to methods of preparing compressed explosive charges from explosives (this term including powders) in the divided state (that is to say in powdery or granular state) and it is more particularly but not exclusively concerned with the packing of such charges in projectiles such as shells, rockets and bombs.

The chief object of the present invention is to provide a method of this kind which is better adapted to meet the requirements of practice than those used at the present time.

It consists chiefly in mixing with the explosive intended to form the charge a resin in the fluid state capable of hardening at a temperature relatively little higher than ordinary temperature, in giving the mixture a divided form, in heating this mixture in the divided state in such manner as to start the resin hardening reaction (this operation being preferably carried out with the mixture in the form of layers of small thickness), in charging this mixture in the usual manner and in allowing the hardening reaction to proceed.

I will now describe in a more detailed fashion the method according to my invention as applied to the charging of a projectile with compressed explosive.

It is known that shells are generally charged by means of automatic machines capable of introducing into every shell a given volume of explosive. Such machines generally include a reciprocating member which, in one of its end positions, receives the explosive from a hopper or the like, and in the other of these positions brings a port located in its bottom opposite a piston or punch which forces the explosive into the shell.

To permit such an operation, the substances used for charging must comply with the following physical conditions:

(l) The same volume of the substance must always correspond to the same weight. Therefore, the explosive in the divided state must, on the one hand have a regular grain size and on the other hand it must be capable of flowing freely through the passages and conduits provided in the automatic machine.

(2) The substance must be suificiently plastic to permit a perfect filling of the shell body, with a substantially uniform distribution of the rate of compression Whatever In particular, in the case of shells having an ogive of great height, where the opening at the top of the ogive is of a diameter much smaller than the inner diameter of the cylindrical portion of the shell body, the plasticity must be such that the explosive can flow back into the annular space comprised between the side walls of the punch and the inner wall of the shell body.

(3) The compressed explosive charge thus obtained must be compact and homogeneous.

As above stated, in order to obtain an explosive substance which complies with these conditions, I make use of a method which comprises mixing with the explosive a resin in the fluid state capable of hardening at a temperature relatively little above ordinary temperature, giving the mixture a granular (or powdery) form, heating the granular mixture to start the resin hardening reaction, then charging a projectile with the mixture and allowing the hardening reaction to proceed.

In this way, the hardening, or at least a partial hardening, of the resin contained in the superficial layer of the grains, which hardening is achieved by the heating intended to start the hardening reaction, maintains the cohesion of the explosive grains and the said layer facilitates the sliding of the grains both on one another and along the guiding walls. Once the mass of explosive has been packed in the shell, it hardens gradually from the outside toward the inside, so as to form a homogeneous block of high mechanical resistance.

Concerning the nature of the resin, it must be such that the temperature at which its hardening reaction takes place is sufliciently low to avoid the risk of decomposition or deterioration of the explosive mixed therewith. As a rule, the resin must have a hardening temperature lower than 100 C. and preferably ranging from 60 to C.

Furthermore, the resin should not disengage water or volatile products when it is hardening.

Among the many types of resins which comply with these conditions, the most advantageous seem to be the mixed polyesters of diacids and of dialcohols, to which may be added products having an influence upon the viscosity such as monomer styrolene. The different compositions of esters of this kind permit of obtaining, after polymerization, substances the hardness and plasticity of which vary within wide limits for instance from those corresponding to ebonite to those corresponding to Indiarubber.

I may mention by way of example the resins sold under the trademark Rhodester which are substantially linear polyhydric alcohol esters of an unsaturated polybasic acid material of the maleic type mixed with a liquid substituted-ethylene body of resin-forming characteristics which is co-polymerizable and miscible therewith. The product designated as Rhodester 1108 contains 30% of styrene and 21.8% of reactive double links other than those with styrene.

In order to reduce the time of hardening or of polymerization of such a resin, the addition of catalysts is practically necessary and that of activators is often useful.

The resins are most often sold on the market with suitable catalysts and activators or accelerators. Otherwise, the manufacturers of these resins give all the indications as may be desired concerning said catalysts, activators and accelerators.

I may cite by way of example, in particular in the case of mixed polyesters of diacids and dialcohols, as catalysts:

Methylethylketone peroxide sold out he market in solution in methyl phthalate,

Cyclohexanone peroxide sold on the market in solution in methyl or butyl phthalate,

Cumene hydroperoxide and benzoyl peroxide sold on the market in the moist state or in the form of a pasty solution in benzyl benzoate, butyl phthalate or tricresylphosphate;

And as activators: cobalt octoate, diethylaniline, and dimethylaniline.

Concerning the amount of resin to be added to the explosive substance, proportions ranging from 5 to 10% and preferably substantially equal to 6% by weight of the explosive substance are generally suitable and do not substantially alter the characteristics of the explosive.

In order to give the mixture the desired granular or powdery state, it generally sufiices, provided the starting explosive is in the dry granular or powdery state, to pass the intimate mixture obtained by stirring the explosive and the resin through a sieve of suitable characteristics.

Concerning the preliminary heating, it is advantageously effected on thin layers of the substance, obtained for instance by spreading said substance on glass plates so as to reduce the time necessary for said heating as much as possible in view of the bad heat transmission properties of the resin and explosive mixture. Heating may be carried out in a conventional hot air oven or in w an infra-red ray oven or again by dielectric losses;

The substance is charged in the usual manner, the only supplementary precautionto be taken being to use the mixture while the resin present therein is sufficiently plastic, that is to say within a time after heating which generally does not exceed 48 hours.

I will now describe examples of the preparation of a compressed charge from a mixture of hexogen and aluminum in powdery state.

For one kilogram of charge material the composition is as follows:

' Gr. Hexogen+aluminum powder- 950 Rhodester 50 Catalyst 1 Activator 0.5

The granular product is heated at 50 C. for 4 hours in an air circulation oven, then it is cooled and once more passed through the sieve.

I thus obtain a partial polymerization of the resin, I

essentially on the surface of the grains. The granular material is relatively hard but it becomes rather pasty if a it is crushed. It must be used within 48 hours from the time it has left the oven.

' Theigranular material is poured into the funnels of the machine and charged into the shells in several steps. Distribution by means of sliding elements takes place easily and uniformly.

' If a shell which has been charged some days previously is sawed, it is found that the whole of themass has set into a very hard block which is perfectly homogeneous 'and compact, polymerization facilitated by the effect of the pressure having gradually taken place inside the shell.

Such a process was applied with the same advantageous results by using on the one hand other explosives or explosive mixtures such as penthrite, tolite, melinite, cresylite (which compositions are defined in Marshall, Dictionary of Explosives P. Blakistons Son & Co., Philadelphia, 1920), perchlorated powders and on the other hand other polyester resins or polyester resin mixtures.

The method according to the present invention may be modified to comply with particular requirements; in particular the characterics of the granular product that is obtained may be modified,

Either by varying the proportion of resin,

Or by raising or lowering the temperature or duration of the heating step,

Or by modifying the amounts of accelerator or catalyst, or the nature of said substances,

Or by modifying the characteristics of the resin, since some resins, as above stated, may become very hard whereas others take the consistency of soft rubber so that it is possible to obtain a plasticity suitable for every particular use.

I can thus obtain any reflux of the material under the punch of the machine and a filling as perfect and homogeneous as possible of a shell of any shape whatever.

When applying the conditions of the method above described, I may also prepare explosive charges having the following compositions:

(a) Penthrite 900 Rhodester 1108 resin 100 Cobalt octo 2 Methylethylketone peroxide- 1 (b) Tolite 900 Rhodester 1108 resin 100 Cobalt octoate 2 Methylethylketone peroxide 1 (c) Tolite 950 Rhodester 11108 resin 50 Cobalt octoate l Methylethylketone peroxide 0.5

Still within the conditions of the method above described, I may prepare propellent charges and in particular solid propergols having for instance the following compositions:

(d) Rhodester resin gr 15 Ammonium perchlorate gr Cobalt octoate cm. 0.150 Methylethylketone peroxide cm. 0.3

(e) Ammonium perchlorate gr 900 Rhodester resin gr 7 Dimethylaniline gr 1 Benzoyl peroxide gr 2 (f) Ammonium perchlorate gr 850 Rhodester resin gr Dimethylaniline gr 1.5 Benzoyl peroxide gr 3 What I claim is:

g l. A method of forming an explosive charge in a pro jectile comprising mixing an explosive from the group consisting of hexogen, tolite, melinite, cresylite, pentaerythrite tetranitrate, and ammonium perchlorate powder with a liquid thermosetting resin to form a paste, said resin being unreactive with the explosive and having a hardening temperature substantially below that at which the explosive decomposes, dividing the pasty mixture into grains, heating the grains to said hardening temperature to harden the surface of each while the interior of each remains in a pasty state, and before setting up of the resin occurs compacting a charge of the semi-hardened grains in the projectile, such setting up thence proceeding in the projectile.

2. A method according to claim 1 wherein the grains Z are spread in a thin layer over a surface before being heated to said hardening temperature.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF FORMING AN EXPLOSIVE CHARGE IN A PROJECTILE COMPRISING MIXING AN EXPLOSIVE FROM THE GROUP CONSISTING OF HEXOGEN, TOLITE, MELINITE, CRESYLITE, PENTAERYTHRITE TETRANITRATE, AND AMMONIUM PERCHLORATE POWDER WITH A LIQUID THERMOSETTING RESIN TO FORM A PASTE, SAID RESIN BEING UNREACTIVE WITH THE EXPLOSIVE AND HAVING A HARDENING TEMPERATURE SUBSTANTIALLY BELOW THAT AT WHICH THE EXPLOSIVE DECOMPOSES, DIVIDING THE PASTRY MIXTURE INTO GRAINS, HEATING THE GRAINS TO SAID HARDENING TEMPERATURE TO HARDEN THE SURFACE OF EACH WILE THE INTERIOR OF EACH REMAINS IN A PASTY STATE, AND BEFORE SETTING UP OF THE RESIN OCCURS COMPACTING A CHARGE OF THE SEMI-HARDENED GRAINS IN THE PROJECTILE, SUCH SETTING UP THENCE PROCEEDING IN THE PROJECTILE. 